The present invention relates generally to external sensors, and, more particularly, to an automatic analog selection circuit for facilitating the reading of external sensors having differing outputs.
Sensors are used to detect and/or monitor a variety of parameters, such as, but not limited to, vibration, acceleration, temperature, humidity, acidity, turbidity, the presence and/or concentration of one or more chemicals or gasses, flow, altitude, geographic location, direction or heading, thickness, corrosion rate, color, level, angular velocity, speed, pressure, pulse rate, or any other desired parameter. The sensor converts such a detected and/or monitored parameter into a proportional electrical signal which may be used for a variety of applications. As an example application, the electrical signal may be supplied to a controller in communication with one or more valves to, for example, control fluid flow of a system.
Because most applications use input types which often differ from sensor outputs, additional hardware is typically used to convert the raw sensor electrical output to a signal compatible with the input of the desired application. For example, a pressure transmitter translates low-level analog electrical outputs from a pressure sensor to higher-level electrical signals that are suitable for transmission and processing. The hardware employed depends on the type of raw sensor output. For example, a sensor outputting an electrical signal of 4-20 milliamps (mA) may employ the use of one particular circuit for conversion, while a sensor outputting an electrical signal of 0-5 volts (V) may employ the use of another separate conversion circuit. Consequently, separate hardware circuitry would need to be employed in order to use different sensor types, which can be time consuming, inefficient, and costly.
Accordingly, there is a need for a system that receives various inputs in a single circuit, and, based on the type of sensor used, automatically selects an appropriate analog input to convert the sensor's output signal to a compatible signal for the desired application.